Component oxidized by plasma electrolysis and method for the production thereof

ABSTRACT

Surface-oxidized, metallic components or semifinished products and corresponding planar components and methods for producing such components and/or semifinished products and corresponding components are disclosed. Such objects may be used, for example, in exterior skin parts of a motor vehicle, such as hoods, car roofs, car doors, fenders and/or side frames, baking trays, or baths. One object is to propose methods for producing surface-oxidized components or semifinished products that have an at least partially oxidized surface. The disclosed methods are suitable for mass production. Some example methods involve applying a surface layer comprising Al, Mg, Ti and/or Zr to a metallic substrate, and then performing plasma electrolytic oxidation of the surface layer. The metallic substrate may be cut to length and formed into a component or semifinished product before or after the plasma electrolytic oxidation. At least one part of the surface layer may be less than 200 μm.

The invention relates to a method for producing a surface-oxidized, metallic component or semi-finished product, to the use thereof and to corresponding planar components, in particular exterior skin parts of a motor vehicle, such as hoods, car roofs, car doors, fenders and/or side frames, friction linings and/or abrasive layers, bearing materials, products from the roasting and/or baking tray sector as well as cooking utensils, in the building sector in the form of roof coverings, wall and/or ceiling paneling, in the lamp and/or radiant heater industry, for combustion chamber, turbine and/or furnace linings as well as exhaust gas systems, heat shields, offshore uses or uses in the sanitary sector, such as shower trays, baths, flushing tables/basins, claddings for washing machines and/or laundry driers as well as components and/or claddings in the electrical industry and/or electronic entertainment systems, heat sinks for electronic components, such as, for example, for LEDs and/or electronic power systems, for improving twill sound insulation and/or sound insulation on components stimulated by vibration and/or exposed to noise, in pipeline construction, in particular with a view to the flow through of highly corrosive and/or abrasive media, stirring and/or mixing devices exposed to wear and claddings and/or devices for conveying sandy and/or sharp-edged bulk goods, as well as surfaces which come into contact with foodstuffs in the foodstuffs industry and also biocompatible, wear-resistant layers in medical prosthetics and/or medical technology, as well as measures which from the constructional aspect necessitate an all-over or partial increase in the buckling resistance, buckling strength, flexural strength, surface hardness and/or wear resistance of components.

Surface finishes of metallic substrates are known. For example, enamel has been known as a protective covering for a long time. During enameling the objects are provided with a layer of enamel by dipping or spraying and then fired at 800 to 850° C. Enamel layers can indeed be applied to many substrates, for example also steel. However, the enamel layers can be easily damaged and are therefore very susceptible to impact. In addition, anodizing is known for aluminum substrates. During anodizing an electrolytic oxidation of aluminum is used to produce an aluminum oxide layer on the aluminum substrate in a controlled manner. The anodized surfaces are of a comparatively high hardness. For hardnesses of more than 400 HV thicker layers are required, which have an increased brittleness. Plasma electrolytic oxidation of aluminum is moreover known, in particular plasma electrolytic oxidation of thin layers of aluminum which have been applied to a steel substrate by the PVD or CVD process. Extremely high hardnesses can be produced with plasma electrolytic oxidation (PEO) or MAO (micro arc oxidation). It is moreover known from “Galvanotechnik May 2012”, “Dunne keramische Schichten aus thermischen and anodischen Prozessen”, T. Lampke et al. pages 934 et seq. to coat blasted steel substrates with an aluminum material by arc or flame spraying and then to oxidize the surface by plasma electrolysis, so that at least partially a fused ceramic is produced on the surface. Plasma electrolytic oxidation can produce layer hardnesses of up to 2,000 HV. However, PVD and CVD processes are not suitable for mass production. There is furthermore the problem that components and semifinished products as a rule have to pass through forming processes.

On the basis of this it is therefore an object of the present invention to propose a method for producing surface-finished components or semifinished products which have an at least partially surface-finished surface, wherein the method is suitable for mass production in spite of the required forming steps. It is moreover an object of the invention to propose advantageous uses and advantageous components.

According to a first teaching of the present invention the object is achieved by a method for producing a surface-finished, metallic component or semifinished product comprising the following method steps:

-   -   providing a strip-like or sheet-like metallic substrate,     -   subsequently applying at least in some regions at least one         surface layer, on one or both sides, comprising an alloy of one         or more of the group of the following metals: Al, Mg, Ti or Zr,     -   carrying out at least in some regions, in particular a         continuous plasma electrolytic oxidation of the surface layer         applied to the substrate and subsequently optionally cutting to         length and forming the coated substrate to give the component or         semifinished product, wherein the thickness of the part of the         surface layer oxidized by plasma electrolysis is less than 5 μm,         preferably less than 3 μm,         or     -   optionally cutting the substrate to length and forming the         substrate to give the component or semifinished product,     -   subsequently carrying out at least in some regions a plasma         electrolytic oxidation of the surface layer applied to the         component or semifinished product, wherein the thickness of the         part of the surface layer oxidized by plasma electrolysis is 5         μm to 200 μm, in particular up to 50 μm, preferably up to 30 μm.

According to the invention a strip-like substrate is understood as meaning a substrate which can be provided in the form of a strip, for example wound up as a coil. A sheet-like substrate is a planar, conventionally rolled substrate, the thickness of which is considerably smaller than the width or length thereof. The semifinished product differs from the component in that the semifinished product according to the present invention is subjected to further method steps, also, for example, forming steps. Due to the sequence of the method steps, depending on the thickness of the layer converted by plasma electrolysis, a particularly economical production can be provided.

The plasma electrolytic oxidation at least in some regions can be carried out at low surface layer thicknesses of less than 5 μm, preferably less than 3 μm, both on the strip-like metallic substrate, in particular continuously, and on the sheets coated piece-wise, before these are subjected to forming. At higher surface layer thicknesses oxidized by plasma electrolysis of from 5 μm to 200 μm, in particular up to 50 μm, preferably up to 30 μm, the plasma electrolytic oxidation must be carried out after the forming. However, the fact that the individual working steps up to the plasma electrolytic oxidation of a part of the surface layer can be carried out particularly economically, for example with strip-like substrates preferably continuously, can also be utilized here. The plasma electrolytic oxidation of the surface is carried out in the electrolyte with significantly higher voltages compared with anodizing. A plasma discharge arises in the electrolyte bath, which causes the plasma electrolytic oxidation of the surface. The oxides of the alloys of the elements Al, Mg, Ti and Zr are distinguished by their particular hardness and corrosion resistance, wherein aluminum alloys are very inexpensive and nevertheless can provide very high hardnesses in the form of their oxides. By the plasma discharge oxide layers are established which, compared with anodizing, for example, are a virtually pore-free, closed layer and are responsible for the improved corrosion protection properties and the higher hardness. It has been found that in particular planar components, that is to say sheet-like substrates, but also strip-like substrates can be converted into a fused ceramic in a large quantity by plasma electrolysis with a sufficient production rate such that a mass production is possible and economical.

According to a first embodiment of the invention the application of the surface layer of the substrate, on one or both sides, comprising an alloy of one or more of the following metals: Al, Mg, Ti or Zr is preferably carried out by hot dip coating or a roll plating of the substrate. Hot dip coating is suitable in particular for coating strip-like substrates with surface layers on both sides. With roll plating coatings on one side with a surface layer comprising an alloy of one of the following metals: Al, Mg, Ti or Zr can also be produced. However, coating on both sides by roll plating is of course also possible. Both aluminum, aluminum alloys, aluminum/magnesium alloys, magnesium, magnesium alloys, magnesium/aluminum alloys and optionally foreign admixtures of e.g. iron, zinc, titanium, vanadium, chromium, cobalt, and/or manganese can be used in the hot dipping bath. Both processes are suitable for the mass production of coated metallic substrates. Metallic substrates coated in strip form are preferably produced by this process.

A substrate of steel, high-grade steel, a nickel-based alloy (superalloy) or another non-ferrous alloy is preferably provided, wherein the steel substrate can optionally be coated with a metallic coating based on Zn, ZnAl, AlZn, ZnMg. In addition to steels protected against corrosion with a metal layer, such as, preferably, carbon steels, high-grade steels, heat-resistant and highly corrosion-resistant high-grade steels or also tool steels are also possible. Nickel-based alloys or also other non-ferrous alloys, such as, for example, alloys which comprise no substantial constituents of the metals Al, Mg, Ti and/or Zr, are likewise suitable as a substrate for the surface coating and the subsequent plasma electrolytic oxidation of the surface layer applied.

According to a further embodiment of the method, a substrate of steel having a thickness of at most 3.0 mm, in particular at most 1.5 mm, preferably at most 0.8 mm, particularly preferably at most 0.5 mm, is provided. In spite of the low thickness of the steel substrates, the components oxidized by plasma electrolysis have a relatively high hardness and, due to the oxide layer, a relatively high E modulus, which in the end leads to a relatively high buckling resistance and buckling strength, so that a further reduction in weight, for example in vehicle construction, is thus possible. The layer thickness of the coating in the case of hot dip coating is 10 μm to at most 50 μm, preferably up to at most 30 μm. The layer thickness of the coating in the case of roll plating is 20 μm to at most 200 μm, preferably up to at most 100 μm.

According to a further embodiment of the invention after application of the surface layer on one or both sides the strip-like substrate is wound up to a coil in order to be fed to the next working steps, for example the cutting to length and forming or the plasma electrolytic oxidation. By this means further economic advantages result in the production of the surface-oxidized, metallic components or semifinished products.

If an aluminum alloy having a maximum of 11 wt. % of Si is used for applying the surface layer of the metallic substrate, an inexpensive metallic substrate coated by hot dipping can be provided which via the plasma electrolytic oxidation can provide outstanding wear resistances and surface hardnesses. The surface coating with a corresponding aluminum alloy is moreover proven technologically in mass production. In particular, the composition of the aluminum alloy ensures that a particularly good adhesion to the surface of steel substrates is guaranteed.

Finally, the method is further configured such that after the production of the component or semifinished product having a surface layer oxidized by plasma electrolysis at least in some regions, this is fed to at least a further surface treatment step. It is conceivable, for example, that the surfaces of the component or of the semifinished product are subjected to an organic and/or an inorganic coating step, for example in the form of lacquering, glazing, for example a color-imparting ceramic glaze, metallizing and/or a coating with Teflon, so that additional functional properties, wherein for example a particularly low adhesion in the case of a Teflon coating, can be provided.

As already stated above, the components or semifinished products produced have properties which are to be particularly emphasized. The surface hardness of the surface layers oxidized by plasma electrolysis at up to 2,000 HV is extremely high, so that the surfaces of the components or semifinished products are particularly wear-resistant. The oxide layer moreover is virtually pore-free in structure, so that a very good corrosion and heat resistance of the treated surfaces is produced. According to a further teaching of the present invention the use of the components or semifinished products produced by the method according to the invention in turbine, power plant and engine construction, in offshore construction, exhaust gas, furnace and automobile construction, in the sanitary sector and also in medical technology and in the abovementioned sector is proposed.

In a preferred use the component is a baking tray which has a surface layer oxidized by plasma electrolysis on one or both sides. It has been found that due to their extreme heat resistance and wear resistance surface layers oxidized by plasma electrolysis are particularly suitable for use as industrial baking trays, but also for domestic use. At the same time the high hardness of the surface layer allows a further reduction in the wall thicknesses of the steel substrate due to the improved buckling strength, buckling resistance and flexural strength, so that the baking trays themselves have a relatively low thermal capacity.

A further use according to the invention is provided by the use of the component or semifinished product for an exterior skin part of a motor vehicle, such as a hood, a car roof, a car door, a fender and/or a side frame. The extreme surface hardness and also the increased buckling resistance, buckling strength and flexural strength allow, as already mentioned for the baking trays, the wall thicknesses of the steel substrates to be reduced and therefore a saving in weight to be achieved, without a loss in buckling strength, buckling resistance and flexural strength having to be accepted.

As a further use in the sanitary sector correspondingly surface-oxidized baths, flushing basins, sinks and also shower trays which have a significantly harder surface than and therefore are not so susceptible to impact as enameled surfaces are conceivable. The surface-oxidized components and semifinished products can readily be provided with an organic and/or inorganic layer or subjected to further surface treatment steps.

According to a further teaching of the present invention the object described is provided by a planar component, in particular an exterior skin part of a motor vehicle, such as a hood, a car roof, a car door, a fender and/or a side frame, a baking tray, a flushing basin, a sink, a shower tray or a bath in that the planar component has a layer, oxidized by plasma electrolysis at least in some regions, of an alloy of at least one of the metals Al, Mg, Ti or Zr.

As already stated above, the excellent surface properties of the regions of the planar component oxidized by plasma electrolysis with the further potential saving in weight render possible extremely high wear resistances or corrosion and heat resistances. For example, savings in weight are conceivable for exterior skin parts of a motor vehicle, such as, for example, for hoods, car roofs, car doors, fenders and/or side frames. In the case of the baking tray, on the other hand, not only the buckling resistance, buckling strength and flexural strength are of primary importance, but also at the same time the increased wear resistance and corrosion resistance with the reduced weight. Finally, in the case of a bath, a flushing basin and/or a shower tray which has a layer oxidized by plasma electrolysis at least in some regions it is advantageous that this is significantly more wear-resistant than and therefore has considerable advantages over conventionally enameled baths or, for example, shower trays and also can be produced by a more economical process. The abovementioned components which have a layer oxidized by plasma electrolysis at least in some regions also have considerable advantages over the conventionally produced components.

According to a further embodiment of the component according to the invention, the component has at least a sheet of steel, high-grade steel, a nickel-based alloy (superalloys) or another non-ferrous alloy. It is common to all the sheets that the surface layer of an alloy of the following metals Al, Mg, Ti or Zr applied provide, due to the plasma electrolytic oxidation, extremely wear-resistant, corrosion-resistant surfaces which can extend significantly the profile of properties of the materials used for the sheets.

If the component has a thickness of the layer oxidized by plasma electrolysis of less than 5 μm, preferably less than 3 μm, it is possible to form the component only after the plasma electrolytic oxidation of the surface layer, so that a particularly more economical production process can be ensured.

If the thickness of the layer oxidized by plasma electrolysis is 5 μm to 200 μm, in particular up to 50 μm, preferably up to 30 μm, on the other hand, a particularly high protection against corrosion and at the same time an extreme hardness of the surface combined with high protection against wear can be provided.

In order to provide further functional properties of the surfaces of the components or semifinished products, the component has a further surface coating at least in some regions on the layer oxidized by plasma electrolysis. This further coating can be, for example, an organic and/or inorganic layer, e.g. a lacquering, a glazing, a metallizing and/or a coating of Teflon. Since the surfaces oxidized by plasma electrolysis are particularly wear-resistant, these are suitable, for example, in particular for sanitary articles of large surface area, such as, for example, baths or shower trays, but also for parts from the sectors of the white, brown and red goods or from the abovementioned sectors. Domestic appliances, for example refrigerators, washing machines or toasters, are conventionally called white goods. However, the extremely wear-resistant and corrosion-resistant surfaces and the reduced weights or the improved buckling resistance, buckling strength and flexural strength of the components correspondingly surface-oxidized by plasma electrolysis are also advantageous for brown goods, electronic entertainment goods and red goods, namely good in the heating technology sector.

The invention is to be explained in more detail in the following text with the aid of embodiments in combination with the drawing. The drawing shows in

FIG. 1 a diagram of the method steps for producing a surface-oxidized metallic component according to an embodiment of the present invention,

FIG. 2, 3 two embodiments for surface coating of the metallic substrate according to two embodiments,

FIG. 4 and FIG. 5 a diagram of embodiments for methods for producing surface-oxidized, metallic components having a layer oxidized by plasma electrolysis of high layer thickness and low layer thickness and

FIGS. 6 to 10 diagrams of four different embodiments of the components according to the invention.

FIG. 1 firstly shows in a very diagrammatic form the various method steps of embodiments of the method according to the invention. In method step 1 a strip-like or sheet-like metallic substrate, for example a strip or sheet of steel, high-grade steel, a nickel-based alloy (superalloy) or another non-ferrous alloy, is first provided, wherein, for example, the steel substrate is optionally coated with a metallic coating based on Zn, ZnAl, AlZn or ZnMg for protection against corrosion. A strip-like metallic substrate, for example a steel strip having a thickness of at most 3.0 mm, in particular at most 1.5 mm, preferably at most 0.8 mm, particularly preferably at most 0.5 mm, is preferably provided, for example in the form of a coil.

In method step 2 a surface layer comprising an alloy of one or more of the following metals: Al, Mg, Ti or Zr, for example an AlSi alloy, is then applied to the metallic substrate on one or both sides. Embodiments of method step 2 are shown in FIGS. 2 and 3.

Depending on whether by the plasma electrolytic oxidation at least in some regions of the surface layer applied an oxidized surface layer of less than 5 μm, preferably less than 3 μm or more than 5 μm to, for example, 200 μm, in particular up to 50 μm, preferably up to 30 μm is to be produced by plasma electrolytic oxidation, the further method steps differ. For a low thickness of the surface layer oxidized by plasma electrolysis of less than 5 μm, according to method step 3 a the plasma electrolytic oxidation is carried out, for example, on the strip-like substrate after the surface coating thereof, preferably in a continuous process. A sheet-wise plasma electrolytic oxidation of the surface layer applied is of course also possible.

After the strip-like plasma electrolytic oxidation the correspondingly surface-oxidized strip is optionally cut to length according to method step 3 b and according to method step 3 c is formed, with the surface layer oxidized by plasma electrolysis, to give a component, for example a baking tray 4. In principle, the strip-like strip oxidized by plasma electrolysis can also first be wound up to a coil in order to be fed to the next process steps.

If a thickness of the surface layer oxidized by plasma electrolysis of from 5 μm to 200 μm is produced on the surface-coated substrate, a strip-like substrate is first optionally cut to length in step 3 a′ and fed to a forming step 3 b′ which brings the substrate into the end form of the component or semifinished product. In the case of the sheet-like surface-coated substrate working step 3 a′ can also be omitted. The plasma electrolytic oxidation of the surface layer applied to the component is then carried out in step 3 c′ to give the finished end product, for example in the form of a baking tray 4.

The process of plasma electrolytic oxidation 3 a or 3 c′ is conventionally carried out in an aqueous electrolyte, wherein the substrate or component to be oxidized is poled anodically and is led into the electrolyte together with a counter-electrode. The initially purely chemically induced passive layer grows with application of the potential between the anodically poled substrate or component and the cathode. The potential is increased further, so that the passive layer is broken down locally at a breakdown voltage. Plasma chemistry solid state reactions take place here, which are visible by sparks. A composite layer of metal and ceramic is produced by the chemical reaction of the oxidized metal with the oxygen split off by hydrolysis. In this context the plasma chemistry solid state reactions as a rule take place at the points with the lowest local resistance, so that the surface is covered with a continuous, homogeneous layer, since all the thin layers provided with a low local resistance are gradually exposed to a plasma chemistry solid state reaction.

For example, an aluminum alloy layer can be after-treated by plasma electrolysis via a pulsed alternating current having a current density of from 30 to 80 A/dm², preferably 50 A/dm². The electrolyte can contain a concentration of 1-5 g/l, preferably 3 g/l of Na₂SiO₃ and 2-7 g/l, preferably 5 g/l of KOH. The layer thickness of the part of the surface layer oxidized by plasma electrolysis can then be established via the duration and the current strength. All the metals of the surface coating Al, Mg, Ti and Zr can form extremely hard oxide layers during plasma electrolytic oxidation, which lead to the preferred properties, for example an extremely high hardness of the surface layer.

For cost reasons aluminum alloys, for example, which furthermore can also provide very high hardnesses, are preferred.

FIG. 2 shows a diagram of a first embodiment of a method for applying a surface layer, for example an aluminum alloy. The substrate 5, for example a substrate of steel having a thickness of at most 3.0 mm to, for example, at most 0.5 mm, is unwound from a coil 6 and fed to a pretreatment 7. The pretreated steel substrate 5 is then led via deflection rolls into a hot dipping bath 9 in which, for example, an aluminum alloy having a maximum of 11 wt. % of silicon and the balance of aluminum and unavoidable impurities is present. When the strip is immersed in the hot dipping bath 9 the aluminum alloy remains adhering to the steel substrates and produces a uniform surface layer in this way. The layer thickness is established on the emerging side on both sides of the surface of the substrate via blow-off devices, which are not shown. In treatment step 10 the strip is after-treated, so that it can then be wound up to a coil 11 or alternatively cut to length in sheets 12.

Alternatively to this, the surface coating can also be carried out by roll plating, which is shown in diagram form in FIG. 3. The strip-like steel substrate 5 is first provided on a coil 6. Foils made of the metal alloy envisaged for the surface coating, for example an alloy of Al, Mg, Ti or Zr, are additionally provided as foils 13 and 14. The foils 13 and 14 and the steel substrate are conventionally pretreated before the roll plating and heated to the roll temperature and fed to the working rolls 15. After the roll plating the surface-coated substrate 5 is again provided on a coil 11 or as sheets 12 cut to length and if appropriate subjected to diffusion annealing. In contrast to the hot dipping process, with roll plating the substrate 5 can also be roll plated merely only on one side. Both processes can be used for economical production of large amounts of coated substrates 5, in particular steel substrates.

FIG. 4 shows a diagram of the further method steps 3 a′, 3 b′ and 3 c′. The coated substrate 5 is provided in a coil 11 and unwound. Since it is envisaged to produce a plasma electrolytic oxidation from 5 μm to 200 μm thick, the surface-coated substrate 11 is first formed in a forming step 16. A simple forming step to give a baking tray having depressions is shown, for example, here. The forming can be carried out, for example, in strip form, wherein the cutting to length into individual baking trays 17 is carried out after the forming step 16. It is of course conceivable to carry out cutting to length of the strip-like substrate 5 before the forming to give a baking tray.

Alternatively to this, FIG. 4 also shows the sheets 12 which are fed to the forming step 16, so that a baking tray 17, for example, can also again be produced from the individual sheets. The baking tray 17 is then subjected to a plasma electrolytic oxidation in an electrolyte bath. Finally, the surface of the baking tray 17 is provided with a surface layer of from 5 μm to 200 μm oxidized by plasma electrolysis and as a surface-oxidized baking tray 17′. Still further surface treatment steps can follow here, for example a lacquering, a glazing or a coating with a Teflon layer. The latter is appropriate for use as a baking tray, in order to prevent the sticking of baking residues. In the industrial baking sector the baking trays conventionally coated with Teflon are used, which are exposed to enormous abrasion in the harsh environment and as a result the Teflon layer becomes detached after a short time. In order not to replace the baking trays after brief exposure to stresses, these must be re-coated with Teflon, wherein they are conventionally subjected to sandblasting for complete removal of the depleted Teflon layer. Conventional baking trays can be re-used only 1 to 2 times. Baking trays according to the invention oxidized by plasma electrolysis withstand several sandblasting processes, for example, and due to their wear-resistant surface can be coated with Teflon and re-used at least 5 times and more often.

Alternatively to this, FIG. 5 shows a strip-like processing of the surface-coated substrate 5. The surface-coated substrate 5 is again provided in a coil 11 and unwound from this. The substrate 5 then runs through an electrolyte bath 19 in which, as in electrolyte bath 18, electrodes 20 are provided. In the electrolyte bath the surface coating of the substrate 5 is oxidized in a layer thickness of less than 5 preferably less then 3 μm thickness, by plasma electrolytic oxidation. In this context the surface layer oxidized by plasma electrolysis is so thin that the strip-like substrate is initially coilable and can readily be fed to a forming process, for example the forming step 16, and the forming of the surface-coated substrate 5 including the part of the surface layer oxidized by plasma electrolysis is carried out. The strip-like substrate can be cut to length, for example, before the forming step 16. The baking tray 17″ produced has a significantly lower layer thickness oxidized by plasma electrolysis. The baking tray 17″ can also be subjected to further surface treatments as already described.

As an embodiment which is not shown, a strip-like substrate oxidized according to the invention by plasma electrolysis can also be fed to a roll profiling process.

FIGS. 6, 7, 8, 9 and 10 now show further embodiments of the component and the use thereof. FIG. 6 shows, for example, a diagram of a perspective view of an exterior skin part of a motor vehicle in the form of a roof 21. FIG. 7 shows in a further perspective diagram an embodiment in the form of a hood 22. FIG. 8 likewise shows a planar component of an embodiment in the form of a baking tray 23. In the case of baking trays, for example, an additional Teflon coating can ensure that as little baking residues as possible stick to the baking tray. However, for the washing machine 24 shown in diagram form in FIG. 9 the surface of the coated steel substrate at least partially oxidized by plasma electrolysis can also provide advantageous properties, for example in that the scratch resistance and corrosion resistance, for example of the cladding or housing, are increased significantly. FIG. 10 shows a bath 25 which is particularly impact-resistant and scratch-resistant in construction due to the surface oxidation and can be produced economically with less outlay than comparable enameled baths.

Depending on the intended use, a perforation and/or stamping, which are not shown, can be carried out, for example, on the semifinished product before the plasma electrolytic oxidation. In order to protect bare edges against corrosion, an alloy of a metal from Al, Mg, Ti or Zr can subsequently be applied, preferably sprayed on, in this region so that a continuous layer oxidized by plasma electrolysis can form.

Alternatively, on a semifinished product before the plasma electrolytic oxidation at places which serve, for example, for connection to further components, in particular in vehicle construction, can be covered with suitable agents, for example with materials having a breakdown voltage of at least 20 kV/mm, for example a ceramic. By this means it is possible to carry out welding, in particular resistance welding and/or fusion welding, as well as soldering in these regions, since the covered region is not converted into a ceramic, electrically insulating layer during the plasma electrolytic oxidation.

It has been found that by using surface coatings which can be used on a large industrial scale on strip-like or sheet-like substrates the use of layers oxidized by plasma electrolysis and the particular properties thereof with respect to wear resistance, heat stability and corrosion resistance opens up further fields of use, for example also in motor vehicle construction. For example, the material thickness of the steel substrate can be lowered further via the increased buckling strength, buckling resistance and flexural strength. This also applies to baking trays in which the thickness of the steel substrate is proportional to the energy required for baking the baked goods. 

1.-15. (canceled)
 16. A method for producing a surface-oxidized, metallic component, the method comprising: providing a metallic substrate that is strip-like or sheet-like; applying a surface layer at least in some regions on one or both sides of the metallic substrate, wherein the surface layer comprises an alloy of at least one of aluminum, magnesium, titanium, or zirconium; and performing one of: carrying out at least in some regions a plasma electrolytic oxidation of the surface layer applied to the metallic substrate, then cutting to length and forming the coated metallic substrate into a component, wherein a thickness of a part of the surface layer oxidized by plasma electrolysis is less than 5 μm; or cutting to length and forming the metallic substrate into a component, then carrying out at least in some regions a plasma electrolytic oxidation of the surface layer applied to the component, wherein a thickness of a part of the surface layer oxidized by plasma electrolysis is 5-200 μm.
 17. A method for producing a surface-oxidized, metallic component, the method comprising: providing a metallic substrate that is strip-like or sheet-like; applying a surface layer at least in some regions on one or both sides of the metallic substrate, wherein the surface layer comprises an alloy of at least one of aluminum, magnesium, titanium, or zirconium; and carrying out at least in some regions a plasma electrolytic oxidation of the surface layer applied to the metallic substrate, wherein a thickness of a part of the surface layer oxidized by plasma electrolysis is less than 200 μm.
 18. The method of claim 17 wherein applying the surface layer to the metallic substrate occurs by way of hot dip coating or roll plating.
 19. The method of claim 17 wherein the metallic substrate that is provided comprises steel, high-grade steel, a nickel-based alloy or superalloy, or some other nonferrous alloy, the method further comprising coating the metallic substrate with a metallic coating based on at least one of Zn, ZnMg, ZnAl, or AlZn.
 20. The method of claim 17 wherein the metallic substrate that is provided comprises steel and has a thickness of at most 3.0 mm.
 21. The method of claim 17 further comprising winding up the metallic substrate on a coil after applying the surface layer.
 22. The method of claim 17 wherein the surface layer comprises an aluminum alloy having a maximum of 11 percent by weight silicon.
 23. The method of claim 17 further comprising feeding a component formed from the metallic substrate to a further treatment step.
 24. The method of claim 17 further comprising using a component formed from the metallic substrate in at least one of turbine construction, power plant construction, engine construction, offshore construction, exhaust gas construction, furnace construction, automobile construction, or a sanitary sector.
 25. The method of claim 24 wherein the component is a baking tray and has on one or both sides surface layers oxidized by plasma electrolysis.
 26. The method of claim 24 further comprising using the component as an exterior skin part for at least one of an automobile, an automobile hood, an automobile roof, an automobile door, an automobile fender, or an automobile side frame.
 27. A planar component comprising a layer that has been oxidized by plasma electrolysis at least in some regions, wherein the layer comprises an alloy of at least one of aluminum, magnesium, titanium, or zirconium.
 28. The planar component of claim 27 for use as an exterior skin part for at least one of an automobile, an automobile hood, an automobile roof, an automobile door, a baking tray, or a bath.
 29. The planar component of claim 27 further comprising a sheet of steel, high-grade steel, a nickel-based alloy or superalloy, or another non-ferrous alloy.
 30. The planar component of claim 27 wherein a thickness of the layer oxidized by plasma electrolysis is less than 5 μm.
 31. The planar component of claim 27 wherein a thickness of the layer oxidized by plasma electrolysis is 5-200 μm.
 32. The planar component of claim 27 further comprising a surface coating disposed on the layer oxidized by plasma electrolysis. 